Dynamic differentiated link adaptation for ultra-wideband communication system

• US 20050201446A1
• Filed: 03/08/2005
• Published: 09/15/2005
• Est. Priority Date: 03/09/2004
• Status: Active Grant

• Current Assignee: New Jersey Institute of Technology
• Original Assignee: New Jersey Institute of Technology
• Inventors: Bar-Ness, Yeheskel, Diaz, Jordi
• Granted Patent: US 7,386,045 B2
• Time in Patent Office: Days
• US Class Current: 375/130
• CPC Class Codes: H04B 1/7176 Data mapping, e.g. modulation
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04B 1/719 Interference-related aspects

Abstract

Optimum usage of time diversity and significantly higher data rates are achieved by utilizing an adaptive Ultra-wideband impulse radio (UWB IR) transmission scheme based upon information about the channel state at a particular time instant. Through the use of channel state information, the transmission scheme is adjusted for the particular channel state. In particular, the system is adapted dynamically for each user by varying the number of pulses transmitted per bit in response to the channel state. The channel state is a dynamic parameter of the transmission system that is typically measured or estimated by the receiver. An adaptation element responds to the channel state information to determine a desired number of pulses per bit to be utilized in a transmission channel for subsequent UWB IR communication. This desired number of pulses per bit is then supplied to and used by an adaptive transmitter for subsequent transmission by a particular mobile station.

Claims

1. Apparatus for an ultra wide bandwidth (UWB) impulse radio (IR) communications system wherein user information bits are modulated to include, in part, a plurality of pulses N_s for each information bit, the apparatus comprising:

means responsive to a communication signal on a particular user link associated with a desired user for determining channel state information therefrom;

means responsive to said channel state information for adaptively varying a modulation parameter so that data throughput on said user link is substantially optimized, the modulation parameter being a measure of the number of pulses per user information bit, N_s^opt.

2. The apparatus as defined in claim 1 further comprising means for transmitting said modulation parameter N_s^opt to a remote location.

3. The apparatus as defined in claim 2 further comprising means responsive to at least the modulation parameter N_s^opt supplied by the adaptively varying means for modulating the user information bits in accordance with the adaptively varied modulation parameter, N_s^opt.

4. The apparatus as defined in claim 1 wherein the channel state information is selected from the group consisting of an average signal-to-noise ratio per pulse and an instantaneous signal-to-noise ratio per pulse.

5. The apparatus as defined in claim 4 wherein the means for adaptively varying further includes means for calculating N_s^opt as:

N_s^opt≈

SNR_opt/{circumflex over (ξ

)},

where {circumflex over (ξ

)} is the determined channel state information and SNR_opt is a constant value determined as follows;

${\mathrm{SNR}}_{\mathrm{opt}}=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{Min}}<br><br>{\int <br><br>}_{{\mathrm{\xi <br><br>}}_{\min }}^{{\mathrm{\xi <br><br>}}_{\max }}<br><br>{\left(N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)-\frac{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{\xi <br><br>}}\right)}^2<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>\mathrm{\xi <br><br>}.$

6. The apparatus as defined in claim 1 further comprising means for quantizing the number of pulses per bit N_s^opt to one of a particular set of values in a desired range.

7. The apparatus as defined in claim 4 wherein the means for adaptively varying further includes means for computing N_s^opt in response to a value of the channel state information ξ

as follows;

$N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{N_s}{\mathrm{Max}}<br><br>\text{\hspace{1em}<br><br>}<br><br>S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right).$

where S(Ns,ξ

) is a throughput function defined as;

$S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)=\frac{1}{T_f·<br><br>N_s}·<br><br>{\left(1-Q<br><br>\left(\sqrt{N_s<br><br>\mathrm{\xi <br><br>}}\right)\right)}^{\frac{T_r}{T_f<br><br>N_s}}$

for T_r and T_f as UWB IR system parameters, where T_r is time duration of a data block and T_f is time duration of a data frame.

8. The apparatus as defined in claim 7 further comprising means for quantizing the channel state information to one of a particular set of values in a desired range.

9. Apparatus for an ultra wide bandwidth (UWB) impulse radio (IR) communications system wherein user information bits are modulated to include, in part, a plurality of pulses N_s for each information bit, the apparatus comprising:

means for receiving channel state information from a remote location related to a particular link associated with a desired user;

means responsive to said channel state information for adaptively varying a modulation parameter so that data throughput on said user link is substantially optimized, the modulation parameter being a measure of the number of pulses per user information bit, N_s^opt.

10. The apparatus as defined in claim 9 further comprising means for transmitting said modulation parameter N_s^opt to a remote location.

11. The apparatus as defined in claim 10 further comprising means responsive to at least the modulation parameter N_s^opt supplied by the adaptively varying means for modulating the user information bits in accordance with the adaptively varied modulation parameter, N_s^opt.

12. The apparatus as defined in claim 9 wherein the channel state information is selected from the group consisting of an average signal-to-noise ratio per pulse and an instantaneous signal-to-noise ratio per pulse.

13. The apparatus as defined in claim 12 wherein the means for adaptively varying further includes means for calculating N_s^opt as:

$N_s^{\mathrm{opt}}\approx <br><br>{\mathrm{SNR}}_{\mathrm{opt}}/\widehat{\mathrm{\xi <br><br>}},$

where {circumflex over (ξ

)} is the determined channel state information and SNR_opt is a constant value determined as follows;

${\mathrm{SNR}}_{\mathrm{opt}}=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{Min}}<br><br>{\int <br><br>}_{{\mathrm{\xi <br><br>}}_{\min }}^{{\mathrm{\xi <br><br>}}_{\max }}<br><br>{\left(N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)-\frac{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{\xi <br><br>}}\right)}^2<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>\mathrm{\xi <br><br>}.$

14. The apparatus as defined in claim 9 further comprising means for quantizing the number of pulses per bit N_s^opt to one of a particular set of values in a desired range.

15. The apparatus as defined in claim 12 wherein the means for adaptively varying further includes means for computing N_s^opt in response to a value of the channel state information ξ

as follows;

$N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{N_s}{\mathrm{Max}}<br><br>\text{\hspace{1em}<br><br>}<br><br>S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)$

where S(Ns,ξ

) is a throughput function defined as;

$S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)=\frac{1}{T_f·<br><br>N_s}·<br><br>{\left(1-Q<br><br>\left(\sqrt{N_s<br><br>\mathrm{\xi <br><br>}}\right)\right)}^{\frac{T_r}{T_f<br><br>N_s}}$

for T_r and T_f as UWB IR system parameters, where T_r is time duration of a data block and T_f is time duration of a data frame.

16. The apparatus as defined in claim 15 further comprising means for quantizing the channel state information to one of a particular set of values in a desired range.

17. A method for dynamically differentiated link adaptation in an ultra wide bandwidth communication system wherein user information bits are modulated to include, in part, a plurality of pulses N_s for each information bit, the method comprising the steps of:

acquiring channel state information related to a particular communication link in the system;

adaptively varying, in response to said channel state information, a modulation parameter so that data throughput on said user link is substantially optimized, the modulation parameter being a measure of the number of pulses per user information bit, N_s^opt.

18. The method as defined in claim 17 further comprising the step of transmitting said modulation parameter N_s^opt to a remote location.

19. The method as defined in claim 18 further comprising the step of means modulating, in response to at least the modulation parameter N_s^opt in the adaptively varying step, the user information bits in accordance with the adaptively varied modulation parameter, N_s^opt.

20. The method as defined in claim 17 wherein the channel state information is selected from the group consisting of an average signal-to-noise ratio per pulse and an instantaneous signal-to-noise ratio per pulse.

21. The method as defined in claim 20 wherein the step of adaptively varying step further includes the step of calculating N_s^opt as:

$N_s^{\mathrm{opt}}\approx <br><br>{\mathrm{SNR}}_{\mathrm{opt}}/\widehat{\mathrm{\xi <br><br>}},$

where {circumflex over (ξ

)} is the determined channel state information and SNR_opt is a constant value determined as follows;

${\mathrm{SNR}}_{\mathrm{opt}}=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{Min}}<br><br>{\int <br><br>}_{{\mathrm{\xi <br><br>}}_{\min }}^{{\mathrm{\xi <br><br>}}_{\max }}<br><br>{\left(N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)-\frac{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{\xi <br><br>}}\right)}^2<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>\mathrm{\xi <br><br>}.$

22. The method as defined in claim 17 further comprising the step of quantizing the number of pulses per bit N_s^opt to one of a particular set of values in a desired range.

23. The method as defined in claim 20 wherein the step of adaptively varying step further includes the step of computing N_s ^opt in response to a value of the channel state information ξ

as follows;

$N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{N_s}{\mathrm{Max}}<br><br>\text{\hspace{1em}<br><br>}<br><br>S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)$

where S(Ns,ξ

) is a throughput function defined as;

$S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)=\frac{1}{T_f·<br><br>N_s}·<br><br>{\left(1-Q<br><br>\left(\sqrt{N_s<br><br>\mathrm{\xi <br><br>}}\right)\right)}^{\frac{T_r}{T_f<br><br>N_s}}$

for T_r and T_f as UWB IR system parameters, where T_r is time duration of a data block and T_f is time duration of a data frame.

24. The method as defined in claim 23 further comprising the step of quantizing the channel state information to one of a particular set of values in a desired range.

25. Method for dynamically differentiated link adaptation in an ultra wide bandwidth (UWB) impulse radio (IR) communications system wherein user information bits are modulated to include, in part, a plurality of pulses N_s for each information bit, the method comprising the steps of:

receiving channel state information from a remote location related to a particular link associated with a desired user;

adaptively varying, in response to said channel state information, a modulation parameter so that data throughput on said user link is substantially optimized, the modulation parameter being a measure of the number of pulses per user information bit, N_s^opt.

26. The method as defined in claim 25 further comprising the step of transmitting said modulation parameter N_s^opt to a remote location.

27. The method as defined in claim 26 further comprising the step of means for modulating, in response to at least the modulation parameter N_s^opt in the adaptively varying step, the user information bits in accordance with the adaptively varied modulation parameter, N_s^opt.

28. The method as defined in claim 25 wherein the channel state information is selected from the group consisting of an average signal-to-noise ratio per pulse and an instantaneous signal-to-noise ratio per pulse.

29. The method as defined in claim 28 wherein the adaptively varying step further includes the step of calculating N_s^opt as:

$N_s^{\mathrm{opt}}\approx <br><br>{\mathrm{SNR}}_{\mathrm{opt}}/\widehat{\mathrm{\xi <br><br>}},$

where {circumflex over (ξ

)} is the determined channel state information and SNR_opt is a constant value determined as follows;

${\mathrm{SNR}}_{\mathrm{opt}}=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{Min}}<br><br>{\int <br><br>}_{{\mathrm{\xi <br><br>}}_{\min }}^{{\mathrm{\xi <br><br>}}_{\max }}<br><br>{\left(N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)-\frac{{\mathrm{SNR}}_{\mathrm{opt}}}{\mathrm{\xi <br><br>}}\right)}^2<br><br>\text{\hspace{1em}<br><br>}<br><br>d<br><br>\mathrm{\xi <br><br>}.$

30. The method as defined in claim 25 further comprising the step of means for quantizing the number of pulses per bit N_s^opt to one of a particular set of values in a desired range.

31. The method as defined in claim 28 wherein the step of adaptively varying step further includes the step of computing N_s^opt in response to a value of the channel state information ξ

as follows;

$N_s^{\mathrm{opt}}<br><br>\left(\mathrm{\xi <br><br>}\right)=\arg <br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{N_s}{\mathrm{Max}}<br><br>\text{\hspace{1em}<br><br>}<br><br>S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)$

where S(Ns,ξ

) is a throughput function defined as;

$S<br><br>\left(N_s,\mathrm{\xi <br><br>}\right)=\frac{1}{T_f·<br><br>N_s}·<br><br>{\left(1-Q<br><br>\left(\sqrt{N_s<br><br>\mathrm{\xi <br><br>}}\right)\right)}^{\frac{T_r}{T_f<br><br>N_s}}$

for T_r and T_f as UWB IR system parameters, where T_r is time duration of a data block and T_f is time duration of a data frame.

32. The method as defined in claim 31 further comprising the step of quantizing the channel state information to one of a particular set of values in a desired range.